Semiconductor module and power conversion device

ABSTRACT

One method of achieving the above subjects is by connecting a block member  14 , which is connected to the side opposite to that of a semiconductor chip  11  having insulating substrates  12  and  13  connected to the top and bottom of the semiconductor chip  11 , to a block member  15  across an laminated structure constituted by the semiconductor chip  11  and the insulating substrates  12  and  13.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor module and a powerconversion device using the same.

Some types of power conversion devices comprise a semiconductor modulein which chip-like semiconductor devices are mounted in packaged ICform. A large majority of power conversion devices, however, comprise asemiconductor module in which semiconductor devices are mounted as theyare. The latter is intended to improve the cooling effect of thesemiconductor module by directly releasing the heat emitted from thesemiconductor devices.

Examples of the products known as semiconductor modules of thisconventional type are disclosed in Japanese Laid-Open Patent PublicationNo. Hei 10-56131. Various products designed so that the heat emittedfrom the respective semiconductor chips is released from the twoprincipal faces of each semiconductor chip are proposed in JapaneseLaid-open Patent Publication No. Hei 10-56131. These products include,for example, a semiconductor module having each semiconductor chipsandwiched between insulating substrates and having these insulatingsubstrates further sandwiched between copper plates so that the heatemitted from the semiconductor chip is released from the two principalfaces thereof.

SUMMARY OF THE INVENTION

For the power conversion devices used under a severe heat-cycleenvironment, such as the power conversion device mounted in anautomobile, as the standards pertaining to power supplies are tightened,the magnitude of the current flowing through semiconductor devicesincreases and this, in turn, increases the heat emitted from thesemiconductor devices and makes the heat cycle even severer.

It is therefore demanded that the cooling performance of thesemiconductor modules constituting the power conversion device should befurther improved over the cooling performance of conventionalsemiconductor modules.

The present invention is to provide a semiconductor module that can beimproved in cooling performance. The present invention is also toprovide a highly reliable, compact, and inexpensive power conversiondevice that can maintain normal operation even when used under a severeheat-cycle environment.

In order to achieve the above, the present invention features asemiconductor module in which one of thermal-conductive membersconnected to the opposite side to the semiconductor device side of eachinsulating substrate connected to either the top or bottom of thesemiconductor device is connected to the other of the thermal-conductivemembers, across the laminated section formed by the semiconductorelement and the insulating substrates.

The present invention also features a semiconductor module in which oneof thermal-conductive members connected to the opposite side to thesemiconductor device side of each electroconductive member connected toeither the top or bottom of the semiconductor device via an insulatingmember is connected to the other of the thermal-conductive members,across the laminated section formed by the semiconductor element, theelectroconductive members, and the insulating members.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view showing the configuration of an inverterdevice as a first embodiment of the present invention;

FIG. 2 is a cross-sectional view of the section II–II′ when seen fromthe direction of the arrow in FIG. 1;

FIG. 3 is a cross-sectional view of the section III–III′ when seen fromthe direction of the arrow in FIG. 1;

FIG. 4 is a cross-sectional view showing in enlarged form theconfiguration of one phase in FIG. 2;

FIG. 5 is a cross-sectional view showing in enlarged form theconfiguration of the semiconductor chip of FIG. 4;

FIG. 6 is a cross-sectional view showing the materials composition ofthe electroconductive adhesive agent used to connect two components ofthe inverter device of FIG. 1;

FIG. 7 is a cross-sectional view showing the materials composition of anelectroconductive adhesive agent as a comparative example of FIG. 6;

FIG. 8 is a circuit diagram showing the circuit composition of theinverter device of FIG. 1;

FIG. 9 is a top plan view showing the configuration of another inverterdevice as a second embodiment of the present invention;

FIG. 10 is a cross-sectional view of the section X–X′ when seen from thedirection of the arrow in FIG. 9; and

FIG. 11 is a cross-sectional view of the section XI–XI′ when seen fromthe direction of the arrow in FIG. 9; and

FIG. 12 is a cross-sectional view showing in enlarged form theconfiguration of one phase in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention is described below inaccordance with FIGS. 1 to 8. FIG. 8 shows the circuit composition ofthe power conversion device pertaining to the present embodiment.

The power conversion device in the present embodiment is intended to bemounted in the motor-driving system of an automobile (for example, amotor-driving system for an electric automobile or a hybrid automobile,or a motor-driving system for automotive motor loads such as an airconditioner and brakes), and this power conversion device is describedbelow taking as an example an inverter device 100 by which the DC powerfrom a battery 200 (operating at, for example, a charging voltage of 42V) is to be converted into three-phase AC power and then supplied to anAC motor 300 (for example, a synchronous motor, an induction motor, orthe like).

The inverter device 100 is constructed so that the DC power of thebattery 200 that has been supplied via a positive-pole DC bus 110 and anegative-pole DC bus 120 is first converted into AC power, for eachphase, during the switching operation of the MOS-FETs 171, 172, 181, and183 controlled by the gate control signal 151 of a control circuit block150, and then supplied to the AC motor 300 via the AC output buses 161to 163 corresponding to each phase. More specifically, conversioncircuits 131 to 133 are constituted by the MOS-FETs 171 to 173 whichform an upper arm 141, and the MOS-FETs 181 to 183 which form a lowerarm 142.

The conversion circuit 131 of a u-phase comprises the MOS-FET 171 of theupper arm 141 and the MOS-FET 181 of the lower arm 142. The drain sideof the MOSFET 171 is connected to the positive-pole DC bus 110, and thesource side is connected to the AC output bus 161. The source side ofthe MOS-FET 181 is connected to the negative-pole DC bus 120, and thedrain side is connected to the AC output bus 161.

The conversion circuit 132 of a v-phase comprises the MOS-FET 172 of theupper arm 141 and the MOS-FET 182 of the lower arm 142. The drain sideof the MOSFET 172 is connected to the positive-pole DC bus 110, and thesource side is connected to the AC output bus 162. The source side ofthe MOS-FET 182 is connected to the negative-pole DC bus 120, and thedrain side is connected to the AC output bus 162.

The conversion circuit 133 of a w-phase comprises the MOS-FET 173 of theupper arm 141 and the MOS-FET 183 of the lower arm 142. The drain sideof the MOSFET 173 is connected to the positive-pole DC bus 110, and thesource side is connected to the AC output bus 163. The source side ofthe MOS-FET 183 is connected to the negative-pole DC bus 120, and thedrain side is connected to the AC output bus 163.

Although the present embodiment described above uses MOS-FETs as thesemiconductor devices constituting the conversion circuits, theseconversion circuits can likewise be composed using other switchingelements such as IGBTs or bipolar transistors.

FIGS. 1 to 5 show the configuration of an actual inverter device 100having the circuit composition of FIG. 8. The inverter device 100comprises: a positive-pole semiconductor module 10 forming the upper arm141; a negative-pole semiconductor module 20 forming the lower arm 142;a busbar 30 forming a positive-pole DC bus 110, a negative-pole DC bus120, and AC output buses 161 to 163; a base 50, and; a heat-releasingmember 60.

Although the inverter device 100 further has the control circuit block150 mentioned in connection with FIG. 8, this control circuit block isnot shown in FIGS. 1 to 5. The positive-pole semiconductor module 10,the negative-pole semiconductor module 20, and the busbar 30 arearranged linearly in proximity to each other on the base 50 so that thebusbar 30 is positioned between the positive-pole semiconductor module10 and the negative-pole semiconductor module 20. The heat-releasingmember 60 is connected to the bottom of the base 40. The heat-releasingmember 60 is a fin-like thermal-conductive member made of a metal suchas aluminum.

The positive-pole semiconductor module 10 has three semiconductor chips11 which form the MOS-FETs 171 to 173 mentioned in connection with FIG.8. The negative-pole semiconductor module 20 has three semiconductorchips 21 which form the MOS-FETs 181 to 183 mentioned in connection withFIG. 8.

The semiconductor chips 11 and 21 in the positive-pole semiconductormodule 10 and the negative-pole semiconductor module 20, respectively,are arranged linearly in proximity to each other in a vertical directionwith respect to the orienting direction of the positive-polesemiconductor module 10, the negative-pole semiconductor module 20, andthe busbar 30 (hereinafter, the orienting direction of these threeelements is referred to as the “first direction”, and the direction inwhich the semiconductor chips are arranged is the same as the stretchingdirection of the busbar 30, and is referred to as the “seconddirection”).

Also, in the positive-pole semiconductor module 10 and the negative-polesemiconductor module 20, the semiconductor chips 11 and 21 forming theconversion circuits of the same phase have an opposed relationship inposition with respect to the first direction.

The semiconductor chip 11 is a flat-plate-like structure constituted bytop, bottom, and four sides, and has: a silicon chip 1 consisting of asource electrode 2, a gate electrode 6 (control electrode), and a guardring 7 at top, and a drain electrode 5 at bottom, and; a sourceelectrode connecting member 4 connected to the source electrode 2 viasolder 3.

Although the semiconductor chip 21 has the same construction as that ofthe semiconductor chip 11, both the top and bottom of the semiconductorchip 21 face in the opposite directions to those of the semiconductorchip 11 (that is to say, the semiconductor chip 21 is structurallyrotated through 180 degrees with respect to the vertical direction ofFIG. 5).

A drain electrode is positioned at the top of the semiconductor chip 21,and a source electrode, a gate electrode, and a guard ring arepositioned at bottom. The source electrode connecting member 4 of thesemiconductor chip 21 is a flat-plate-like electroconductive member madeof a metal such as copper. The guard ring 7 is provided at the upper orlower marginal section of the silicon chip 1 and forms the boundarybetween the potential areas at the top and bottom of the silicon chip 1.

The semiconductor chip 11 (21) is sandwiched from the top and bottomthereof (more specifically, the top and bottom of the silicon chip 1),between the insulating substrates 12 and 13 (22 and 23) that arearranged at and connected to the top and bottom of the semiconductorchip 11 (21). The insulating substrates 12 and 13 (22 and 23) areflat-plate-like ceramic members formed from a highly heat-conductivealuminum nitride material or the like.

At the side of the insulating substrate 12 (22) that faces the top ofthe semiconductor 11 (21) (more exactly, the top of the silicon chip 1),in other words, at the connection side with respect to the semiconductor11 (21), a wiring pattern 8 is formed by a metallizing or platingprocess. The side of the insulating substrate 12 that faces the top ofthe semiconductor 11 is connected to the upper side thereof (namely, thesource electrode connecting member 4) via solder 16 so that the wiringpattern 8 is electrically connected to the source electrode connectingmember 4.

The side of the insulating substrate 22 that faces the top of thesemiconductor 21 is connected to the upper side thereof (more exactly,the top of the silicon chip 1) via solder 26 so that the wiring pattern8 is electrically connected to the drain electrode 5. The wiring pattern8 is a thin-plate-like or sheet-like electroconductive member made of ametal, for example, copper.

At the side of the insulating substrate 13 (23) that faces the bottom ofthe semiconductor 11 (21) (more exactly, the bottom of the silicon chip1), in other words, at the connection side with respect to thesemiconductor 11 (21), a wiring pattern 9 is formed by a metallizing orplating process. The side of the insulating substrate 12 that faces thebottom of the semiconductor 11 is connected to the lower side thereof(more exactly, the bottom of the silicon chip 1) via solder 17 so thatthe wiring pattern 9 is electrically connected,to the drain electrode 5.

The side of the insulating substrate 23 that faces the bottom of thesemiconductor 21 is connected to the lower side thereof (more exactly,the source electrode connecting member 4) via solder 16 so that thewiring pattern 9 is electrically connected to the source electrodeconnecting member 4. The wiring pattern 9 is a thin-plate-like orsheet-like electroconductive member made of a metal (for example,copper).

In this way, in the present embodiment, double-side wired structure isimplemented by sandwiching the semiconductor chip 11 (21) between, andfrom the sides facing the tops and bottoms of, the insulating substrates12 and 13 (22 and 23) having the wiring patterns 8 and 9, respectively,formed by metallizing or plating. Thereby, the number of components inboth the positive-pole semiconductor module 10 and the negative-polesemiconductor module 20 is minimized and wireless bonding-lessprocessing is realized.

In the present embodiment, the above-described structure, in turn,minimizes the number of wiring connections between the componentsconstituting the current routes of both the positive-pole semiconductormodule 10 and the negative-pole semiconductor module 20, andsignificantly reduces risks relating to rupture and the like. Accordingto the present embodiment, therefore, the reliability of the inverterdevice 100 can be improved.

A block member 15 (25) is disposed at the opposite side of theinsulating substrate 13 (23) with respect to the semiconductor chip 11(21). The block members 15 and 25 are made of a single, metallic (forexample, copper), heat-conductive flat plate formed in common to boththe positive-pole semiconductor module 10 and the negative-polesemiconductor module 20, and constitute the base 50. The side of theblock member 15 (25) that faces the insulating substrate 13 (23) isconnected to the opposite side thereof with respect to the semiconductorchip 11 (21), via an electroconductive adhesive 19 (29).

Although, in the present embodiment, an example in which the blockmembers 15 and 25 are formed into a single flat plate common to both thepositive-pole semiconductor module 10 and the negative-polesemiconductor module 20 has been described, the block members 15 and 25can also be separately formed for each of the correspondingsemiconductor modules.

A block member 14 (24) is disposed at the opposite side to thesemiconductor chip 11 (21) of the insulating substrate 12 (22). Theblock members 14 and 24 are metallic (for example, copper),thermal-conductive members, and the side of the block member 14 (24)that faces the insulating substrate 12 (22) is connected to the oppositeside thereof with respect to the semiconductor chip 11 (21), via anelectroconductive adhesive 18 (28).

In the block member 14 (24), three through-holes are formed in parallelin a first direction. The laminated structure consisting of thesemiconductor chip 11 (21) and the insulating substrates 12 and 13 (22and 23) is connected to the central section of each through-hole in itsfirst direction. That is to say, the block member 14 (24) is formed intoa single bridge-like or arch-like member so that from an upper wall,side walls provided at both ends of the upper wall in its seconddirection, and two support walls by which the space between the sidewalls is split into three equal spaces in the second direction, theblock member 14 (24) straddles the laminated structure consisting of thesemiconductor chip 11 (21) and the insulating substrates 12 and 13 (22and 23). The side walls and support walls of the block member 14 (24)are connected to the block member 15 (25).

In the three equally split spaces of the block member 14 (24), thelaminated structure consisting of the semiconductor chip 11 (21) and theinsulating substrates 12 and 13 (22 and 23) is stored so as to besandwiched between the block members 14 and 15 (24 and 25) from bothsides of the laminated structure in its laminating direction. The platethickness of the block member 14 (24) is greater than the thickness inthe laminating direction of the laminated structure consisting of thesemiconductor chip 11 (21) and the insulating substrates 12 and 13 (22and 23).

The electroconductive adhesives 18, 19, 28, and 29 are each a mixture ofmetallic pieces (metallic filler) or metal particles and resin. FIG. 6shows the cross-sectional structure of applied and curedelectroconductive adhesives 18, 19, 28, and 29 in the presentembodiment. In the present embodiment, mixtures of epoxy resin 400 andsilver particles 500 having needle-like protrusions are used as theelectroconductive adhesives 18, 19, 28, and 29. As is obvious from thefigure, in the electroconductive adhesives 18, 19, 28, and 29 of thepresent embodiment, adjoining silver particles 500 are closelyintermixed in the epoxy resin 400 and at the same time, the inside ofthe protrusions of the silver particles 500 is filled with the epoxyresin 400 so as not to create a clearance.

Compared with an electroconductive adhesive formed by mixing a globalmetallic filler with resin, the electroconductive adhesives 18, 19, 28,and 29 in the present embodiment enable high electroconductivity to beachieved only by adding a small amount of metallic pieces or metalparticles, and at the same time, high mechanical strength to beobtained. That is to say, to achieve electroconductivity equal to thatused in the present embodiment, the electroconductive adhesive in whicha global-metallic filler 700 and resin 600 are mixed (see FIG. 7) mustbe filled with the metallic filler so as not to create a clearance.

However, since the amount of resin decreases correspondingly, mechanicalstrength will also decrease. Accordingly, to achieve highelectroconductivity with a small amount of metallic pieces or metalparticles and also to obtain high mechanical strength, it is preferablethat such electroconductive adhesives 18, 19, 28, and 29 as used in thepresent embodiment should be used.

Examples of the electroconductive adhesives which contain a metallicfiller having needle-like protrusions are introduced in the July 2001Number of “Electronic Materials” that features electroconductiveadhesives on pages 89–96.

Since it is low in both impedance and thermal resistance, the soldercommonly used for bonding two members of laminated structure isexcellent in electroconductivity and heat conductivity. For an inverterdevice that releases heat from both faces of each semiconductor chip,thermal fatigue exerted on the surface of the solder can also be reducedby distributing the thermal stress.

However, as in the present embodiment, in the case of two-memberconnection of the inverter device in which, as the standards pertainingto power supplies are tightened, the magnitude of the current flowingthrough semiconductor-devices further increases duringautomobile-mounted use under a severe heat-cycle environment, especiallyin the connection of a ceramic insulating substrate and a copper blockmember, there is the fear that the significant difference in linearexpansion coefficient between both will exert thermal fatigue on thesurface of the soldered connection and result in rupture stemming fromthis surface.

For this reason, a bonding agent as low as solder in terms of bothimpedance and thermal resistance and higher than solder in terms ofmechanical strength is required as a bonding agent alternative tosolder.

In the present embodiment, therefore, such electroconductive adhesive asdescribed above is used for two-member connection. Accordingly, in thepresent embodiment, in two-member connection of the inverter device inwhich, as the standards pertaining to power supplies are tightened, themagnitude of the current flowing through semiconductor devices furtherincreases during automobile-mounted use under a severe heat-cycleenvironment, even if the difference in linear expansion coefficientbetween the two members is significant, thermal fatigue exerted on thesurface of the connection can be reduced and the inverter device can bestably operated under a severe heat-cycle environment.

In the present embodiment, therefore, the reliability of the inverterdevice can be improved. In the present embodiment, since the inverterdevice is constructed so that heat is released from both faces of eachsemiconductor chip, it is also possible to further reduce the thermalfatigue exerted on the surface of the connection, and to further improvethe reliability of the inverter device.

Although, in the present embodiment, an example in which anelectroconductive adhesive is used for connection between the insulatingsubstrates 12, 13, 22, and 23, and the block members 14, 15, 24, and 25,has been described, the electroconductive adhesive can also be used forconnection between the insulating substrates 12 and 22 (13 and 23) andthe wiring pattern 8 (9), between the source electrode 2 and sourceelectrode connecting member 4 of the silicon chip 1, and between othersections. Hereby, the reliability of the inverter device can be furtherimproved.

The busbar 30 is formed between the positive-pole semiconductor module10 and the negative-pole semiconductor module 20, and in the center ofthe base 50, by laminating the positive-pole DC busbar 31, thenegative-pole DC busbar 32, the w-phase busbar 33, the v-phase busbar34, and the u-phase busbar 35, in that order, from bottom. An insulatingmember 36 for electrically insulating the contact surfaces between thesesections is provided between the base 50 and the busbar 30 and betweenother busbars. The positive-pole DC busbar 31 and the negative-pole DCbusbar 32 are equivalent to input wiring. The w-phase busbar 33, thev-phase busbar 34, and the u-phase busbar 35 are equivalent to outputwiring.

An external connection terminal section 31 a is formed at one end of thepositive-pole DC busbar 31 in its second section. An external connectionterminal section 32 a is formed at one end of the negative-pole DCbusbar 32 in its second section.

An external connection terminal section 35 a is formed at the other endof the u-phase busbar 35 in its second section. An external connectionterminal section 34 a is formed at the other end of the v-phase busbar34 in its second section. An external connection terminal section 33 ais formed at the other end of the w-phase busbar 33 in its secondsection.

In the busbar 30 that is configured into laminated structure as in thepresent embodiment, the current to the inverter circuit alternatelyflows and the magnetic fields generated by the alternately flowingcurrent offset one another. Hereby, in the present embodiment, thereactance parasitic on the inverter circuit decreases and theovervoltage applied to the semiconductor chips 11 and 21 duringlarge-current switching is suppressed. According to the presentembodiment, therefore, the reliability of the inverter device 100 can beimproved.

Although, in the present embodiment, an example of laminating the busbarcomponents in the order mentioned above has been described, thelamination of the busbar components is not limited to theabove-mentioned order and there is no problem even if the w-phase busbar33, the v-phase busbar 34, and the u-phase busbar 35, the negative-poleDC busbar 32, and the positive-pole DC busbar 31 are laminated in thatorder from bottom.

In this case, however, it is preferable that the top and bottom of eachsemiconductor 11 (silicon chip 1) in the positive-pole semiconductormodule 10 and the top and bottom of each semiconductor 21 (silicon chip1) in the negative-pole semiconductor module 20 should be inverted toprevent intercrossing between the connecting members described later.

One end of a connecting conductor 37 is solder-connected to the wiringpattern 9 of the insulating substrate 13 which is connected to thebottom only of the semiconductor chip 11, among all three semiconductorchips 11 shown in FIG. 1, that is positioned at the left side in thesecond direction.

The other end of the connecting conductor 37 is solder-connected to thepositive-pole DC busbar 31. By these connections, the drain electrode 5of the corresponding semiconductor chip 11 and the positive-pole DCbusbar 31 are electrically connected. One end of a connecting conductor38 is solder-connected to the wiring pattern 8 of the insulatingsubstrate 12 which is connected to the top of the correspondingsemiconductor chip 11.

The other end of the connecting conductor 38 is solder-connected to theu-phase AC busbar 35. By these connections, the base electrode 2 of thecorresponding semiconductor chip 11 and the u-phase AC busbar 35 areelectrically connected. The connecting conductors 37 and 38 areflat-plate-like electroconductive members made of a metal (for example,copper).

One end of a connecting conductor 39 is solder-connected to the wiringpattern 9 of the insulating substrate 23 which is connected to thebottom only of the semiconductor chip 21, among all three semiconductorchips 21 shown in FIG. 1, that is positioned at the left side in thesecond direction. The other end of the connecting conductor 39 issolder-connected to the negative-pole DC busbar 32.

By these connections, the base electrode 2 of the correspondingsemiconductor chip 21 and the negative-pole DC busbar 32 areelectrically connected. One end of a connecting conductor 40 issolder-connected to the wiring pattern 8 of the insulating substrate 22which is connected to the top of the corresponding semiconductor chip21.

The other end of the connecting conductor 40 is solder-connected to theu-phase AC busbar 35. By these connections, the drain electrode 5 of thecorresponding semiconductor chip 21 and the u-phase AC busbar 35 areelectrically connected. The connecting conductors 39 and 40 areflat-plate-like electroconductive members made of a metal, for example,copper.

One end of a connecting conductor 41 is solder-connected to the wiringpattern 9 of the insulating substrate 13 which is connected to thebottom only of the semiconductor chip 11, among all three semiconductorchips 11 shown in FIG. 1, that is positioned centrally in the seconddirection. The other end of the connecting conductor 41 issolder-connected to the positive-pole DC busbar 31. By theseconnections, the drain electrode 5 of the corresponding semiconductorchip 11 and the positive-pole DC busbar 31 are electrically connected.

One end of a connecting conductor 42 is solder-connected to the wiringpattern 8 of the insulating substrate 12 which is connected to the topof the corresponding semiconductor chip 11. The other end of theconnecting conductor 42 is solder-connected to the v-phase AC busbar 34.By these connections, the base electrode 2 of the correspondingsemiconductor chip 11 and the v-phase AC busbar 34 are electricallyconnected. The connecting conductors 41 and 42 are flat-plate-likeelectroconductive members made of a metal,for example, copper.

One end of a connecting conductor 43 is solder-connected to the wiringpattern 9 of the insulating substrate 23 which is connected to thebottom only of the semiconductor chip 21, among all three semiconductorchips 21 shown in FIG. 1, that is positioned centrally in the seconddirection.

The other end of the connecting conductor 43 is solder-connected to thenegative-pole DC busbar 32. By these connections, the base electrode 2of the corresponding semiconductor chip 21 and the negative-pole DCbusbar 32 are electrically connected. One end of a connecting conductor44 is solder-connected to the wiring pattern 8 of the insulatingsubstrate 22 which is connected to the top of the correspondingsemiconductor chip 21.

The other end of the connecting conductor 44 is solder-connected to thev-phase AC busbar 34. By these connections, the drain electrode 5 of thecorresponding-semiconductor chip 21 and the v-phase AC busbar 34 areelectrically connected. The connecting conductors 43 and 44 areflat-plate-like electroconductive members made of a metal, for example,copper.

One end of a connecting conductor 45 is solder-connected to the wiringpattern 9 of the insulating substrate 13 which is connected to thebottom only of the semiconductor chip 11, among all three semiconductorchips 11 shown in FIG. 1, that is positioned at the right side in thesecond direction. The other end of the connecting conductor 45 issolder-connected to the positive-pole DC busbar 31. By theseconnections, the drain electrode 5 of the corresponding semiconductorchip 11 and the positive-pole DC busbar 31 are electrically connected.

One end of a connecting conductor 46 is solder-connected to the wiringpattern 8 of the insulating substrate 12 which is connected to the topof the corresponding semiconductor chip 11. The other end of theconnecting conductor 46 is solder-connected to the w-phase AC busbar 33.By these connections, the base electrode 2 of the correspondingsemiconductor chip 11 and the w-phase AC busbar 33 are electricallyconnected. The connecting conductors 45 and 46 are flat-plate-likeelectroconductive members made of a metal,for example, copper.

One end of a connecting conductor 47 is solder-connected to the wiringpattern 9 of the insulating substrate 23 which is connected to thebottom only of the semiconductor chip 21, among all three semiconductorchips 21 shown in FIG. 1, that is positioned at the right side in thesecond direction.

The other end of the connecting conductor 47 is solder-connected to thenegative-pole DC busbar 32. By these connections, the base electrode 2of the corresponding semiconductor chip 21 and the negative-pole DCbusbar 32 are electrically connected.

One end of a connecting conductor 48 is solder-connected to the wiringpattern 8 of the insulating substrate 22 which is connected to the topof the corresponding semiconductor chip 21. The other end of theconnecting conductor 48 is solder-connected to the w-phase AC busbar 33.By these connections, the drain electrode 5 of the correspondingsemiconductor chip 21 and the w-phase AC busbar 33 are electricallyconnected. The connecting conductors 47 and 48 are flat-plate-likeelectroconductive members made of a metal (for example, copper).

As described above, in the present embodiment, exactly as the busbar 30is disposed between the positive-pole semiconductor module 10 and thenegative-pole semiconductor module 20, the positive-pole semiconductormodule 10, the negative-pole semiconductor module 20, and the busbar 30are arranged linearly in proximity.

According to this configuration, electrical connection between thepositive-pole semiconductor module 10, the negative-pole semiconductormodule 20, and the busbar 30, can be easily established by use of theconnecting conductors 37 to 48. Hereby, in the present embodiment, thenumber of components of the inverter device 100 is reduced and theconfiguration of the inverter device 100 is simplified. According to thepresent embodiment, therefore, the inverter device 100 can be reduced inboth dimensions and costs.

In addition, according to the present embodiment, since the laminatingorder of the elements constituting the busbar 30 is changed according tothe particular configuration of the positive-pole semiconductor module10 and the negative-pole semiconductor module 20, the connectingconductors 37 to 48 do not cross one another between the positive-polesemiconductor module 10, the negative-pole semiconductor module 20, andthe busbar 30.

At the gate electrode 6 of the semiconductor chip 11 (21), a wiringmember 70 that has been inserted from the sections of the block members14 and 24 that are holed in the first direction of the busbar 30, at theopposite side thereof, is connected by a metallic ball 71. Hereby, thewiring member 70 is electrically connected to the date electrode 6.

The wiring member 70 is a thin-plate-like or sheet-likesignal-transmitting member that applies gate control signals 151(switching control signals for turning on and off the MOS-FETs 171–173and 181–183) from the control circuit block 150 to the gates of theMOS-FETs. More specifically, the wiring member 70 is either anelectroconductive member covered with a resin film or anelectroconductive member attached to one side of a resin film. The resinfilm is a flexible film formed from insulating resin. The metallic ball71 is a global, electroconductive, and adhesive member formed fromsolder.

In the present embodiment, such wiring connection as described above isused to connect the gate electrode 6 and the wiring member 70. This isbecause, since, the position of the gate electrode 6 in the areasurrounded by the guard ring 7 provided on one face of the top or bottomof the silicon chip 1 is outer than that of the source electrode 2, itis necessary to ensure the required distance not affecting the electricfield design of the guard ring 7, and at the same time to perform thewiring connection to the gate electrode 6.

Also, in the present embodiment, in order to enable the above-describedwiring connection, electrical connection between the source electrode 2and the wiring patterns 8 and 9 of the insulating substrates 12 and 23is achieved using the following method:

That is to say, the source electrode 2 and the wiring patterns 8 and 9of the insulating substrates 12 and 23 are electrically connected viathe source electrode connecting member 4. And the size of the connectionsurface of the source electrode connecting member 4 is limited to thesize of the electrode surface of the source electrode 2 so that a wiringconnection space can be obtained between the wiring member 70 and thegate electrode 6.

Also, the source electrode connecting member 4 has a plate thicknessthat enables the necessary isolation distance to be obtained between theguard ring 7 and the wiring member 70. Hereby, the necessary space forwiring connection is ensured between the silicon chip 1 and theinsulating substrates 12 and 23.

In the present embodiment, the case that the gate electrode 6 and thewiring member 70 are connected by such wiring connection as describedabove has been set forth. However, if, in the area surrounded by theguard ring 7, the gate electrode 6 is present at an inner position thatthat of the source electrode 2, the need may arise to connect the wiringpatterns 8 and 9 of the insulating substrates 12 and 23 and the sourceelectrode 2 without using the source electrode connecting member 4.

If this is the case, it is preferable that a method be used in which:one end of a lead-out line (electroconductive wire line) having theother end connected to the source electrode 2 is to be pulled out via anotch or hole provided in either the source electrode connecting member4 or the insulating substrates 12 and 23, and while the necessarydistance with respect to the guard ring 7 is being maintained, thelead-out line is to be pulled out and then connected to the wiringmember 70.

According to the present embodiment heretofore described, since aheat-releasing channel is formed at both the top and bottom of thesemiconductor chip 11 (21) by sandwiching this semiconductor chip 11(21) between the insulating substrates 12 and 13 (22 and 23) and blockmembers 14 and 15 (24 and 25) from both the top and bottom of thesemiconductor chip 11 (21), and since the cross-sectional area of theheat flow section of the heat-releasing channel is extended byconnecting the block member 14 (24) to the block member 15 (25) acrossthe laminated structure formed by the semiconductor chip 11 (21) and theinsulating substrates 12 and 13 (22 and 23), a heat stream 80 releasedfrom the top of the semiconductor chip 11 (21) and flowing in onedirection towards the top of the laminating direction of the laminatedstructure is diffused to produce a heat stream 81 flowing in variousdirections with respect to the vertical face to the laminating directionof the laminated structure (in the figure, only the flow of heat in aperpendicular and horizontal direction with respect to the laminatingdirection of the laminated structure is shown). Subsequently, the heatstream 81 is transmitted to the block member 15 (25) and then releasedfrom a heat-releasing structure 60 to the outside together with a heatstream 82 which is released from the bottom of the semiconductor chip 11(21) and flowing towards the bottom of the laminating direction of thelaminated structure.

Hereby, in the present embodiment, the thermal resistance of both thepositive-pole semiconductor module 10 and the negative-polesemiconductor module 20 can be significantly reduced and increases inthe temperatures of both modules can also be significantly reduced.According to the present inventors, it has been possible to empiricallyverify that the thermal resistance of both the positive-polesemiconductor module 10 and the negative-pole semiconductor module 20can be reduced to about ½ of the corresponding conventional value andthat increases in the temperatures of both modules can also be reducedto about ½ of the corresponding conventional values (that is to say,cooling performance can be improved to about twice that of aconventional product).

According to the present embodiment, therefore, by adopting even morecompact semiconductor chips 11 and 21, the positive-pole semiconductormodule 10 and the negative-pole semiconductor module 20 can bedimensionally reduced and increases in the temperatures of both modulescan be controlled to stay within the permissible temperature range ofthe semiconductor chips 11 and 21, even if the amount of current flowingthereinto is increased by the tightening of the standards relating tothe battery 200, the power supply mounted in an automobile.

Accordingly, the present embodiment makes it possible to provide ahighly reliable, compact, and inexpensive inverter device 100 whosenormal operation can be maintained even when used under a severeheat-cycle environment.

In addition, according to the present embodiment, since the block member14 (24) is formed into a bridge shape or an arch shape, thecross-sectional area of the heat flow section of the heat-releasingchannel can be extended within the range that satisfies theautomobile-mounting dimensions of the inverter device 100, withoutextending more than necessary the laminated structure, in its laminatingdirection or its vertical direction, that is formed by the semiconductorchip 11 (21) and insulating substrates 12 and 13 (22 and 23).

Although, an example in which the heat-releasing structure 60 isconnected to the bottom of the base 50 has been described in the presentembodiment, the thermal resistance of both the positive-polesemiconductor module 10 and the negative-pole semiconductor module 20can be further reduced to about ½ of the corresponding conventionalvalue by connecting a similar heat-releasing structure to the tops ofthe block members 14 and 24 as well.

Next, a second embodiment of the present invention is described below inaccordance with FIGS. 9 to 12. FIGS. 9 to 12 show the circuitcomposition of an actual power conversion device. In the presentembodiment, the configuration of the laminated structure insertedbetween the block members 14 and 15 (24 and 25) in the positive-polesemiconductor module 10 (negative-pole semiconductor module 20) differsfrom the configuration described in the first embodiment.

In the second embodiment, the laminated structure made up of thesemiconductor chip 11 (21), the electroconductive members 73 and 74 (83and 84), and the insulating members 75 and 76 (85 and 86), is sandwichedbetween block members 14 and 15 (24 and 25) under a positionalrelationship similar to that of the first embodiment. Theelectroconductive members 73, 74, 83, and 84 are flat-plate-like membersmade of a metal (for example, copper). The insulating members 75, 76,85, and 86 are ceramic flat-plate-like members formed from a materialhigh in heat conductivity, such as an aluminum nitride material.

The side of the electroconductive member 73 that faces the top of thesemiconductor chip 11 is connected to the top (source electrodeconnecting member 4) thereof via solder 16 so as to ensure electricalconnection to the source electrode connecting member 4. The side of theelectroconductive member 74 that faces the bottom of the semiconductorchip 11 is connected to the bottom thereof (more exactly, the bottom ofthe silicon chip 1) via solder 17 so as to ensure electrical connectionto the drain electrode 5.

The side of the electroconductive member 83 that faces the top of thesemiconductor chip 21 is connected to the top (silicon chip 1) thereofvia solder 26 so as to ensure electrical connection to the drainelectrode 5. The side of the electroconductive member 84 that faces thebottom of the semiconductor chip 21 is connected to the bottom (sourceelectrode connecting member 4) thereof via solder 27 so as to ensureelectrical connection to the source electrode connecting member 4.

The side of the insulating member 75 (85) that faces the opposite sideof the electroconductive member 73 (83) with respect to thesemiconductor chip 11 (21) is connected via an electroconductiveadhesive 90 (91) to the opposite side of the electroconductive member 73(83) with respect to the semiconductor chip 11 (21). The side of theinsulating member 76 (86) that faces the opposite side of theelectroconductive member 74 (84) with respect to the semiconductor chip11 (21) is connected via an electroconductive adhesive 92 (93) to theopposite side of the electroconductive member 74 (84) with respect tothe semiconductor chip 11 (21). The electroconductive adhesive 90 to 93are created from the same material as that of the first embodiment, soas to have the same construction as that of the first embodiment.

The side of the block member 14 (24) that faces the opposite side of theinsulating member 75 (85) with respect to the electroconductive member73 (83) is connected via an electroconductive adhesive 94 (95) to theopposite side of the insulating member 75 (85) with respect to thesemiconductor chip 11 (21).

The side of the block member 15 (25) that faces the opposite side of theinsulating member 76 (86) with respect to the electroconductive member74 (84) is connected via an electroconductive adhesive 96 (97) to theopposite side of the insulating member 76 (86) with respect to thesemiconductor chip 11 (21).

The configuration of busbars in the present embodiment differs from theconfiguration of the first embodiment. In the present embodiment, thebusbars are divided into DC-use busbars 51 that constitute input wiring,and AC-use busbars 52 that constitute output wiring, and these two typesof busbars are arranged so as to be orthogonal with respect to oneanother. The DC-use busbars 51 consist of a positive-pole DC busbar 53and a negative-pole DC busbar 54, which are arranged between thelinearly provided structure constituted by the positive-polesemiconductor module 10 and the negative-pole semiconductor module 20.

The positive-pole DC busbar 53 consists of the electroconductive member73 and is formed from a flat-plate-like first section extending from thepositive-pole semiconductor module 10 towards the negative-polesemiconductor module 20 with respect to the direction of arrangement ofboth modules (hereinafter, this direction is referred to as a thirddirection), and a flat-plate-like section extending in a right-angledirection (hereinafter, referred to as a fourth direction) with respectto both the extending direction of the first section and the directionof arrangement of the positive-pole semiconductor module 10 and thenegative-pole semiconductor module 20, between the linearly providedstructure of the positive-pole semiconductor module 10 and negative-polesemiconductor module 20 (in other words, between the block members 14and 24), in such a manner that the cross section in the fourth directionhas a shape of L. An external connection terminal section 53 a is formedat one end of the positive-pole DC busbar 53 in its fourth direction.

The negative-pole DC busbar 54 consists of the electroconductive member83 and is formed from a flat-plate-like first section extending from thenegative-pole semiconductor module 20 towards the positive-polesemiconductor module 10 with respect to the third direction, and aflat-plate-like section extending in the fourth direction at rightangles with respect to the extending direction of the first section,between the linearly provided structure of the positive-polesemiconductor module 10 and negative-pole semiconductor module 20 (inother words, between the block members 14 and 24), in such a manner thatthe cross section in the fourth direction has a shape of L. The secondsection of the positive-pole DC busbar 53 and that of the negative-poleDC busbar 54 overlap in the third direction via an insulating member 55.An external connection terminal section 54a is formed at one end of thenegative-pole DC busbar 54 in its fourth direction.

The AC-use busbars 52 consist of a u-phase busbar 56, a v-phase busbar57, and a w-phase busbar 58. The u-phase busbar 56, the v-phase busbar57, and the w-phase busbar 58 are formed by integrating theelectroconductive member 74 of the positive-pole semiconductor module 10and the electroconductive member 84 of the negative-pole semiconductormodule 20 for each corresponding phase, and each of the three busbars isa fat-plate-like structure extending from the negative-polesemiconductor module 20 towards the positive-pole semiconductor module10 with respect to the third direction, and protruding from thepositive-pole semiconductor module 10 towards the opposite side withrespect to the negative-pole semiconductor module 20.

An external connection terminal section 56 a is formed at the section ofthe u-phase AC busbar 56 that protrudes from the positive-polesemiconductor module 10 towards the opposite side with respect to thenegative-pole semiconductor module 20. An external connection terminalsection 57 a is formed at the section of the v-phase AC busbar 57 thatprotrudes from the positive-pole semiconductor module 10 towards theopposite side with respect to the negative-pole semiconductor module 20.

An external connection terminal section 58 a is formed at the section ofthe w-phase AC busbar 58 that protrudes from the positive-polesemiconductor module 10 towards the opposite side with respect to thenegative-pole semiconductor module 20.

Structurally, other sections are the same as those of the firstembodiment, and are therefore assigned the same numerals as those usedin the first embodiment. For these reasons, description of othersections is omitted.

According to the present embodiment heretofore described, sincesimilarly to the first embodiment, a double-sided heat-releasing channelis formed and the cross-sectional area of its heat flow section isextended, it is possible, similarly to the first embodiment, to reducethe thermal resistance of both the positive-pole semiconductor module 10and the negative-pole semiconductor module 20 to about ½ of thecorresponding conventional value, to reduce increases in thetemperatures of the positive-pole semiconductor module 10 and thenegative-pole semiconductor module 20 to about ½ of the correspondingconventional values, and thus, similarly to the first embodiment, toreduce the dimensions of the positive-pole semiconductor module 10 andthe negative-pole semiconductor module 20 and suppress increases in thetemperatures of both modules.

Accordingly, the present embodiment also makes it possible to provide ahighly reliable, compact, and inexpensive inverter device 100 whosenormal operation can be maintained even when used under a severeheat-cycle environment.

According to the present embodiment, since the DC-use busbars 51 areconstituted using the electroconductive members 73 and 83 whichconstitute the positive-pole semiconductor module 10 and thenegative-pole semiconductor module 20, and since the AC-use busbars 52are constituted using the electroconductive members 74 and 84 whichconstitute the positive-pole semiconductor module 10 and thenegative-pole semiconductor module 20, it is also possible to reduce thenumber of components, compared with that of the first embodiment, andsimplify the configuration of the inverter device 100.

According to the present embodiment, therefore, it is possible toprovide an even more compact and less expensive inverter device 100 thanthat of the first embodiment.

The reference sign mean the following parts:

10 . . . Positive-pole semiconductor module, 11, 21 . . . Semiconductorchips, 12, 13, 22, 23 Insulating substrates, 14, 15, 24, 25 . . . Blockmembers, 20 . . . Negative-pole semiconductor module, 30 . . . Busbar,51 . . . DC-use busbar, 52 . . . AC-use busbar, 60 . . . Heat-releasingmember, 73, 74, 83, 84 . . . Electroconductive members, 75, 76, 85, 86 .. . Insulating members.

According to the present embodiment described above, it is possible toprovide a semiconductor module whose cooling performance can beimproved. According to the present embodiment, it is also possible toprovide a highly reliable, compact, and inexpensive inverter devicewhose normal operation can be maintained even when used under a severeheat-cycle environment.

1. A semiconductor module comprising: a semiconductor device havingelectrodes at both surfaces thereof; insulating substrates electricallyconnected to respective ones of said electrodes, each of said insulatingsubstrates being provided with wiring electrically connected tocorresponding electrodes of said semiconductor device, whereby saidsemiconductor device and said insulating substrate form a laminatedstructure section; a block member made of electrically conductive metal;first means for connecting one face of said block member to one face ofsaid laminated structure section; a heat releasing structure provided onthe other face of said block member; a metallic thermal-conductivemember; second means for connecting said thermal conductive member tothe other face of the laminated structure section within a cavity formedin said thermal-conductive member; wherein, each of said first andsecond means consists of an electrically conductive adhesive; wherein,said thermal-conductive member has a portion that surrounds the cavityand is connected to said block member; wherein, the laminated structuresection is confined within the cavity in such a manner that side facesof the laminated structure section do not touch the block member and thethermal-conductive member; whereby a heat stream from the top of thelaminated structure is released through the thermal-conductive member tosaid block member and said heat releasing structure.
 2. A semiconductormodule according to claim 1, wherein said electrically conductiveadhesive comprises metallic pieces or metallic particles mixed withresin.
 3. A semiconductor module according to claim 2, wherein saidmetallic pieces or said metallic particles have needle-like orpetal-like protrusions and said protrusions are in close contact witheach other in said resin.